Field of the Invention
The present invention relates to the use of at least one extract of a rosacea of the genus Sanguisorba in a cosmetic composition and/or for producing a dermatological composition, with the extract and/or the composition being intended for promoting pigmentation of the skin and/or the body hair and/or the cranial hair, as well as to the use of at least one extract of a rosacea of the genus Sanguisorba as a propigmentation agent and/or simulator of melanogenesis in a cosmetic composition and/or for producing a dermatological composition. The present invention also relates to a cosmetic process for pigmenting the skin and/or the body hair and/or the cranial hair, which process consists in applying, to the skin and/or the body hair and/or the cranial hair, a composition which comprises at least one extract of a rosacea of the genus Sanguisorba.
The color of the cranial hair and the human skin depends on a variety of factors, which, in particular, include the seasons of the year, and the race, sex and age of the individual. Color is principally determined by the concentration in the keratinocytes of melanin, which is produced by the melanocytes. The melanocytes are specialized cells which synthesize melanin using special organelles, i.e. the melanosomes.
The synthesis of melanin, or melanogenesis, is particularly complex and, in outline, involves the following main steps:
Tyrosine.fwdarw.Dopa.fwdarw.Dopaquinone.fwdarw.Dopachrome.fwdarw.Melanin
Tyrosinase (monophenoldihydroxylphenylalanine:oxygen oxidoreductase/EC 1.14.18.1) is the essential enzyme involved in this sequence of reactions. In particular, the enzyme catalyzses the reaction in which tyrosine is transformed into dopa (dihydroxyphenylalanine) and the reaction in which dopa is transformed into dopaquinone.
In the epidermis, the melanocyte is involved in the epidermal melanic unit, which consists of one melanocyte surrounded by approximately 36 neighboring keratinocytes. All individuals, irrespective of phototype, possess approximately the same number of melanocytes in a given area of skin. Ethnic differences in terms of pigmentation are not due to the number of melanocytes but, instead, to the properties of their melanosomes. The melanosomes are aggregated into complexes and are of small size. They are highly specialized organelles whose sole function is to produce melanin. They arise from the endoplasmic reticulum in the form of spherical vacuoles termed premelanosomes. While the premelanosomes contain an amorphous protein substrate, they do not contain any melanogenic enzymes. During maturation of the premelanosome, the amorphous substrate organizes itself into an orientated fibrillar structure along the longitudinal axis of the melanosome. Four stages are distinguished in the development of the melanosome, corresponding to the intensity of the melanization. The melanin is deposited uniformly on the internal fibrillar network of the melanosome, and the opacity of the organelle increases until saturation is reached. As the melanin is synthesized in the melanosomes, the latter move from the perinuclear region towards the ends of the dendrites of the melanocytes. The ends of the dendrites are captured by the keratinocytes, by means of phagocytosis, after which the membranes are degraded and the melanosomes are redistributed in the keratinocytes.
Although the level of melanin varies from one population to another, the quantity of tyrosinase does not vary significantly, and the level of tyrosinase messenger RNAs is identical in white and black skins. The variations in melanogenesis are, therefore, are caused by variations either in the activity of the tyrosinase or in the ability of the keratinocytes to phagocytose the melanosomes.
It is known that, in most populations, obtaining a brown skin color and maintaining a constant cranial hair color are important aspirations.
Furthermore, diseases of the pigmentation exist, such as vitiligo, which is an autoimmune disease which is characterized by the appearance on the skin of white patches which are linked to a defect of pigmentation.
There is, therefore, a genuine need for a product which facilitates and/or improves the pigmentation of the skin and/or of the body hair and/or of the cranial hair.
Numerous solutions have been proposed within the sphere of artificial coloration, involving the provision of exogenous dyes such as DHA, which are supposed to impart to the skin and/or the body hair and/or the cranial hair a color which is as close as possible to the natural color, or in the sphere of natural coloration, involving stimulation of the natural pathways of pigmentation, for example by using active compounds which stimulate melanogenesis with or without the action of UV light such as .alpha.MSH or prostaglandins. For example, publications WO-A-9517161, WO-9511003, WO-A-9501773, WO-A-9404674, WO-A-9404122, EPA-585018, WO-A-9310804, WO-A-9220322 and WO-A-9107945 have proposed solutions which are as varied as compositions which contain a phosphodiesterase inhibitor, and the use of prostaglandins, of DNA fragments and of tyrosine derivatives.
While excellent results have certainly been obtained using the solutions which have been proposed in the prior art, the compounds employed either frequently exhibit significant side-effects or are complex mixtures which lack specificity.